The present invention relates to excretable thermostable enzymes, namely, pullulanase and amylase, that are synthesized by and recoverable from thermophilic, anaerobic bacteria, such as Thermoanaerobacter finii and Thermobacteroides acetoethylicus.
The synthesis of amylolytic enzymes by thermophilic bacteria has been described. In the context of the present invention, amylolytic enzymes denote enzymes that break down starch and pullulan such as amylase and pullulanase respectively. According to published international patent application No. WO 86/01831, when Clostridium thermohydrosulfuricum ATCC 33,223 is cultured batchwise in a culture medium containing 0.5% soluble starch, the enzymes amylase, pullulanase and glucoamylase are formed, but these enzymes are retained intracellularly and are not released into the culture medium; compare also Appl. Envir. Microbiol. 49: 1168-1173 (1985).
According to published international patent application No. WO 86/01832, when Clostridium thermosulfurogenes ATCC 33,743 (same as DSM 2,229 deposited at Deutsche Sammlung von Mikroorganismen) is cultured batchwise in a culture medium with 0.5% soluble starch, the enzymes amylase and glucoamylase are formed, but only amylase is released into the culture medium.
To obtain amylase, pullulanase or both in any significant amounts from these bacteria, therefore, one has to propagate the bacteria, harvest and lyse them, and then separate the amylolytic enzymes from other cellular enzymes.